1. Field of the invention
The present invention relates to a light emitting diode (LED) array, and more particularly to a method of making a semiconductor LED in which an internally emitted light can be efficiently radiated to the outside by forming current injection region and current blocking layer by using the diffusion of zinc.
2. Description of the Prior Art
At a high information-oriented age, as data processing capability of office-automation devices such as computer increases continuously, a printer as its data outputing device also requires high-speed, high-resolution and multi-functions. As a result, for such a requirement, an LED array which is a light source of an optical printer employing an electro-photographic technique is asked for a high optical power and resolution. However, when a radiative area is narrowed to achieve high-resolution, it is difficult to obtain high optical power, therefore, a photoemission efficiency must be enhanced.
FIGS. 1 and 2 show a portion of a known LED array, wherein a reference numeral 1 is a GaAs substrate, 2 is an n-type GaAsP film, 3 is a zinc diffusion region, 4 is an insulating film, 5 is a p-type electrode, and 6 is an n-type electrode, respectively. In case of making a p-n junction by using the zinc diffusion, P-type and n-type semiconductor are of the same material, resulting in a homojunction, therefore a high-speed printing can't be accomplished due to a low optical output power. Recently in order to perform a high-speed printing, the heterojunction structure is studied, as shown in FIG. 2.
Referring now to FIG. 2(A), a known LED array includes a GaAs substrate 11, a p-type GaAlAs radiative layer 12, a GaAlAs transparent layer 13, an n-type cap layer 14, an n-type electrode 15, a p-type electrode 16, and a internal radiative region 17, respectively.
However, in case of comprising the elements in said manner, when a voltage is applied to an element, the internal light-density is high as shown in FIG. 2(B), but the radiative region 17 is formed under the electrode 15, therefore, when the light is radiated to the outside, a great loss is brought due to the disturbance of the electrode 15 as shown in FIG. 2(C).